Waterborne Coating Binders Based on Self-Crosslinking Acrylic Latex with Embedded Inorganic Nanoparticles: A Comparison of Nanostructured ZnO and MgO as Crosslink Density Enhancing Agents

This paper is focused on a simple preparation of functional acrylic latex coating binders comprising embedded nanoparticles originating from ZnO and MgO, respectively, in the role of interfacial ionic self-crosslinking agents. The incorporation of surface-untreated powdered nano-oxides into the coating binder was achieved in the course of the latex synthesis performed by a technique of the two-step emulsion polymerization. By means of this technological approach, latexes comprising dispersed nanoparticles in the content of ca 0.5-1.1 wt % (based on solids) were successfully prepared. For the interfacial covalent self-crosslinking, diacetone acrylamide repeat units were introduced into the latex polymer to ensure functionalities for the subsequent reaction with adipic acid dihydrazide. The latex storage stability and coating performance were compared with respect to the type and concentration of the incorporated nanoparticles. It was determined that all latex coating binders comprising nanoparticles exhibited long-term storage stability and provided interfacially crosslinked transparent smooth coating films of high gloss, excellent solvent resistance, and favorable physico-mechanical properties. Moreover, latexes with embedded nanoparticles, which originated from MgO, manifested a pronounced drop in minimum film forming temperature and provided highly water whitening resistant coating films.